In Normal and Heroic difficulty, only the one listed boss will drop the corresponding tokens.

In LFR difficulty, the one listed boss is the main source of tokens, but all of the first six (Morchok through Warmaster Blackhorn) bosses have a smaller chance of dropping a different token. For example, LFR Yor'sahj mostly drops leg tokens, but has a chance to drop shoulder, chest, leg, and helm tokens.